The present invention relates to quenching apparatus for steel pipes and more particularly to a multi-pipe type quenching apparatus designed to quench a plurality of steel pipes simultaneously.
In the past, there has been known a quenching apparatus for steel pipes (hereinafter simply referred to as pipes) which quenches steel pipes by a so-called inner surface quenching method. In this apparatus, pipes are quenched one by one by clamping the ends of each pipe and supplying water through the pipe and its operating efficiency is low due to the unidirectional cooling which cools the pipe from inside.
To overcome this deficiency, another method has been proposed in which pipes are quenched by the process of immersing each pipe in a water tank. While pipes of large diameters can be quenched satisfactorily by this apparatus, in the case of small-diameter pipes the water is changed into vapor within the pipe so that voids are created and the draining of the water is deteriorated. As a result, each pipe is immersed into the water to quench both the inner and outer surfaces and at the same time the pipe ends are clamped so as to pass the water through the pipe and thereby increase the internal water velocity. However, the required treating time is still long due to the pipes being treated one by one.
Thus, the prior art quenching apparatus are inferior in quenching efficiency and also they are disadvantageous in that the operation of clamping the ends of a pipe for passing the water therethrough causes a bend in the pipe.